In the related art, copper alloy plastic working materials have been used as materials of mechanical components, electric components, articles for daily use, building material, and the like. The copper alloy plastic working material is shaped by subjecting an ingot to plastic working such as rolling, wire drawing, extrusion, groove rolling, forging, and pressing.
Particularly, from the viewpoint of manufacturing efficiency, elongated objects such as a bar, a wire, a pipe, a plate, a strip, and a band of a copper alloy have been used as the material of the mechanical components, the electric components, the articles for daily use, the building material, and the like.
The bar has been used as a material of, for example, a socket, a bush, a bolt, a nut, an axle, a cam, a shaft, a spindle, a valve, an engine component, an electrode for resistance welding, and the like.
The wire has been used as a material of, for example, a contact, a resistor, an interconnection for robots, an interconnection for vehicles, a trolley wire, a pin, a spring, a welding rod, and the like.
The pipe has been used as a material of, for example, a water pipe, a gas pipe, a heat exchanger, a heat pipe, a break pipe, a building material, and the like.
The plate and the strip have been used as a material of, for example, a switch, a relay, a connector, a lead frame, a roof shingle, a gasket, a gear wheel, a spring, a printing plate, a gasket, a radiator, a diaphragm, a coin, and the like.
The band has been used as a material of, for example, an interconnector for a solar cell, a magnet wire, and the like.
Here, as the elongated objects (copper alloy plastic working material) such as the bar, the wire, the pipe, the plate, the strip, and the band, copper alloys having various compositions have been used according to respective uses.
For example, as a copper alloy that is used in an electronic apparatus, an electric apparatus, and the like, a Cu—Mg alloy described in Non-Patent Document 1, a Cu—Mg—Zn—B alloy described in Patent Document 1, and the like have been developed.
In this Cu—Mg-based alloy, as can be seen from a Cu—Mg-system phase diagram shown in FIG. 1, in the case where the Mg content is in a range of 3.3% by atom or more, a solution treatment and a precipitation treatment are performed to allow an intermetallic compound composed of Cu and Mg to precipitate. That is, the Cu—Mg-based alloy can have a relatively high electrical conductivity and strength due to precipitation hardening.
In addition, as a copper alloy plastic working material that is used in a trolley wire, a Cu—Mg alloy rough wire described in Patent Document 2 is suggested. In the Cu—Mg alloy, the Mg content is in a range of 0.01% by mass to 0.70% by mass. As can be seen from the Cu—Mg-system phase diagram shown in FIG. 1, the Mg content is smaller than a solid solution limit, and thus the Cu—Mg alloy described in Patent Document 2 is a solid-solution-hardening type copper alloy in which Mg is solid-solubilized in a copper matrix phase.
Here, in the Cu—Mg-based alloy described in Non-Patent Document 1 and Patent Document 1, a lot of coarse intermetallic compounds containing Cu and Mg as main components are distributed in the matrix phase. Therefore, the intermetallic compounds serve as the starting points of cracking during bending working, and thus cracking tends to occur. Accordingly, there is a problem in that it is difficult to shape a product with a complicated shape.
In addition, in the Cu—Mg-based alloy described in Patent Document 2, Mg is solid-solubilized in a copper matrix phase. Therefore, there is no problem in formability, but strength may be deficient depending on a use.